Stenotic lesions may comprise a hard, calcified substance and/or a softer thrombus material, each of which forms on and within the lumen walls of a blood vessel and restricts blood flow through the lumen. Intra-luminal treatments such as balloon angioplasty (PTA, PTCA, etc,)) stent deployment, atherectomy, and thrombectomy are well known and have proven effective in the treatment of such stenotic lesions. These treatments often involve the insertion of at therapy catheter into a patient's vasculature, which may be tortuous and may have numerous stenoses of varying degrees throughout its length. In order to place the distal end of a catheter at the treatment site, a guidewire is typically introduced and tracked from an incision, through the vasculature, and across the lesion. Then at catheter (e,g., a balloon catheter), perhaps carrying a stent at its distal end, can be tracked over the guidewire to the treatment site. Ordinarily, the distal end of the guidewire is quite flexible so that it can be rotatably steered and pushed through the bifurcations and turns of the typically irregular passageway without damaging the vessel walls.
In some instances, the extent of occlusion of the lumen is so severe that the lumen is completely or nearly completely obstructed, which may be described as a total occluslon. If this occlusion persists for a long period of time, the lesion is referred to as a chronic total occlusion or CTO. Furthermore in the case of diseased blood vessels, the lining of the vessels may be characterized by the prevalence of atheromatous plaque which may form total occusions. The extensive plaque formation of a chronic total occlusion typically has a fibrous cap surrounding softer plaque material. This fibrout cap tray present a surface that is difficult to penetrate with a conventional guidewire, and the typically flexible distal tip of the guidewire may be unable to cross the lesion.
Thus for treatment of total occlusions, stiffer guidewires have been employed to recanalize through the total occlusion. However due to the fibrous cap of thee total occlusion, a stiffer guidewire still may not be able to cross the occlusion. Further, in a CTO there may be a distortion of the regular vascular architecture, such that there may be multiple small non-functional channels throughout the occlusion rather than one central lumen for recanalizaition. Furthermore these spontaneously recanalized channel may be responsible for failers due to their dead-end pathways, which may misdirect the guidewires. Once a “false” tract is created by a guidewire, subsequently attempts to cross the CTO with different guidewires may continue to follow the same incorrect path as it is very difficult to steer subsequent guidewire away from the false tract.
What is needed is a steerable device that aids in directing a guidewire to an optimum approach for crossing a chronic total occlusion CTO, as well as provides support to the guidewire for pushing the guidewire through the CTO.